1. Field of the Invention
The present invention relates to an improvement in a waterproof plug in a connector used to connect electric wires together.
2. Description of the Prior Art
The Applicant has previously proposed a waterproof plug as shown in FIGS. 4 to 6 and 13A, 13B and 13C (Japanese Utility Model Application Laid-open No. 147277/1987).
According to the aforesaid application, a waterproof plug 5 is designed in such a manner that a tubular portion 7a whose inner portion is formed as an electric wire inserting hole 7b is provided at one side thereof with a caulking portion 7c for suppressingly fixing the electric wire together with a caulking member 2a of a connecting terminal 2 and provided at the outer periphery of the other side with a rubber plug 7 formed with an outer tube portion 7d which is capable of fitting to the inner wall of a connector housing 1, and a stabilizing tube 8 formed of a hard rigid resin insulator is provided between the tubular portion 7a and the outer tube portion 7d. An electric wire 3 inserted into the tubular portion 7a is suppressingly fixed by means of the caulking portion 7c of the rubber plug 7 and a caulking element 2a of the connecting terminal 2. The connecting terminal 2 is doubly prevented from disengagement by a flexible stopping arm 4 and a rear holder 6 fitted facing to a flange portion 8a of the stabilizing tube 8.
Recently, with an increase of electric appliances loaded on a vehicle, smaller size of connectors and connecting terminals have been earnestly demanded. If a connector is minimized to meet such demand as described, the rubber plug 7 is also minimized. As shown in FIGS. 5 and 7A, the inner diameter R of the stabilizing tube 8 is slightly larger than the external diameter D of the electric wire 3, and a tubular portion 7a' of the rubber plug 7 becomes extremely thin. The tubular portion 7a' comes into contact with the surface of the electric wire 3 when the latter is inserted, and therefore, the tubular portion 7a' is pulled and tends to be torn inwardly as shown in FIG. 7B. Therefore, there gives rise to a drawback in that the tubular portion 7a' is to generate a difference in level between the tubular portion 7a' and the pleat 7e within the electric wire inserting hole 7b so that a waterproof sealing property is lowered and the insertion of the electric wire is made difficult.
Furthermore, with a recent increase of electric appliances loaded on the vehicle, a number of electric wires are wired within a limited space and therefore, smaller size of connectors and connecting terminals have been earnestly demanded.
In view of the above, as a means to make a waterproof connector smaller, the external diameter of the rubber plug 7 (or a waterproof plug 5) can be made small in order to reduce a lateral pitch. However, a sealing portion (a tubular portion 7a) between the electric wire 3 and the rubber plug 7 and that an outer tube portion 7d between the plug 7 and a housing 1 are in a concentric circular relation, and the rubber plug 7 including the stabilizing tube 8 needs to have a specified thickness in order to maintain the sealing property and the strength. It is noted that even if the stabilizing tube 8 is omitted, the waterproof plug will still function only with the tubular portion 7a of the rubber plug but it is not possible to provide a double engagement of the connecting terminal. Accordingly, it is difficult to minimize the connector having a waterproof plug of the conventional construction.